1. Field of the Invention
The present invention relates to a multilayer circuit having a conductor made up of a superconductive material, and its manufacturing method.
2. Description of the Related Art
Conventionally, multilayer circuits, which are used in electronic equipment, are formed by use of normal conductive materials or semiconductor materials. In the process of manufacturing the multilayer circuits, the formation of a conductive film, coating of a resist, exposure, and etching are performed. However, according to this method, since a non-circuit part is removed by etching, a circuit part is formed to be projected. In a case where the multilayer circuits are formed by this method, the circuit part is formed and an insulating material is embedded in the removed non-circuit part, so that the surface of the circuit is caused to be flat, thereby forming a first circuit layer. Thereafter, a second circuit layer is formed on the first circuit layer in the same manner as the above. Therefore, if the multilayer circuits are formed by the conventional method, the productivity considerably decreases.
The superconductive material exhibits a superconductive phenomenon on cooling to a very low temperature, which is less than the critical temperature (hereinafter called Tc), and an electrical resistance becomes zero, thereby a large amount of current can flow. The application of the superconductive material to the electronic equipments has been widely studied. Particularly, oxide superconductive materials such as Y-Ba-Cu-O system and Bi-Sr-Ca-Cu-O system, which exhibit the superconductive phenomenon near the temperature of liquid nitrogen, has be recently found out, and the practical use of the oxide superconductive materials has been widely made. In accordance with this situation, the development of the multilayer circuits using oxide superconductive materials has been actively made.
However, regarding the above-mentioned superconductive materials, particularly oxide superconductive materials, Tc and a critical current density (hereinafter called Jc) considerably change by a slight difference in a composition or a difference in a crystal orientation. Due to this, to apply the oxide superconductive material to the multilayer circuit, the development of the manufacturing method having the above-mentioned features are required.